This invention relates to a hydraulic power transmission system comprising first and second drive units each including one or more hydraulic motors.
Hitherto, in such a system, no means has been provided to alter the torque automatically and manually by cutting in and out the motors selectively. In order to alter the torque it has invariably been necessary to provide gears, clutches, brakes, etc., except in cases where a fluid flywheel was provided. A fluid flywheel has the disadvantage of being inefficient at low speeds.
It is the object of the present invention to provide a hydraulic power transmission system which overcomes the disadvantages mentioned, and which provides a particularly advantageous method of altering the torque of a motor system comprising a plurality of motors driven from a common hydraulic source.